Allowances usually sit in Division 01. The owner names an amount for an item, and every bidder includes the same amount. The contract adjusts later when the real cost is known.
Example: the documents tell the flooring bidder to carry a stated amount per square yard for carpet material. The owner picks the carpet after award.
Read the allowance section closely. Check what the amount covers. Some allowances cover material only, and labor, freight and markup stay in your base bid. Show the allowance as its own line so the general contractor can see you carried it.